Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy & Astrophysics. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Ohio State University, 2002. / Title from first page of PDF file. Document formatted into pages; contains xxix, 171 p., also contains graphics. Includes abstract and vita. Advisor: Andrew P. Gould. Includes bibliographical references (p. 153-157).

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, August 2001. / Includes bibliographical references. Also available on the Internet.

No description available.

Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Mathematics and Statistics.

Strong gravitational lensing produces multiple distorted images of a background source when it is closely aligned with a mass distribution along the line of sight. The lensed images provide constraints on the parameters of a model of the lens, and the images themselves can be inverted providing a model of the source. Both of these aspects of lensing are extremely valuable, as lensing depends on the total matter distribution, both luminous and dark. Furthermore, lensed sources are commonly located at cosmological distances and are magnified by the lensing effect. This provides a chance to image sources that would be unobservable when viewed with conventional optics. The semilinear method expresses the source modeling step as a least-squares problem for a given set of lens model parameters. The blurring effect due to the point spread function of the instrument used to observe the lensed images is also taken into account. In general, regularization is needed to solve the source deconvolution problem. We use Krylov subspace methods to solve for the pixelated sources. These optimization techniques, such as the Conjugate Gradient method, provide natural regularizing effects from simple truncated iteration. Using these routines, we are able to avoid the explicit construction of the lens and blurring matrices and solve the least squares source optimization problem iteratively. We explore several regularization parameter selection methods commonly used in standard image deconvolution problems, which lead to previously derived expressions for the number of source degrees of freedom. The parameters that describe the lens density distribution are found by global optimization methods including genetic algorithms and particle swarm optimizers. In general, global optimizers are useful in non-linear optimization problems such as lens modeling due to their parameter space mapping capabilities. However, these optimization methods require many function evaluations and iterative approaches to the least squares problem are beneficial due to the speed advantage that they offer. We apply our modeling techniques to a subset of gravitational lens systems from the Sloan Lens ACS (SLACS) survey, and are able to reliably recover the parameters of the lens mass distribution with both analytical and regularized pixelated sources.

Strong gravitational lensing produces multiple distorted images of a background source when it is closely aligned with a mass distribution along the line of sight. The lensed images provide constraints on the parameters of a model of the lens, and the images themselves can be inverted providing a model of the source. Both of these aspects of lensing are extremely valuable, as lensing depends on the total matter distribution, both luminous and dark. Furthermore, lensed sources are commonly located at cosmological distances and are magnified by the lensing effect. This provides a chance to image sources that would be unobservable when viewed with conventional optics. The semilinear method expresses the source modeling step as a least-squares problem for a given set of lens model parameters. The blurring effect due to the point spread function of the instrument used to observe the lensed images is also taken into account. In general, regularization is needed to solve the source deconvolution problem. We use Krylov subspace methods to solve for the pixelated sources. These optimization techniques, such as the Conjugate Gradient method, provide natural regularizing effects from simple truncated iteration. Using these routines, we are able to avoid the explicit construction of the lens and blurring matrices and solve the least squares source optimization problem iteratively. We explore several regularization parameter selection methods commonly used in standard image deconvolution problems, which lead to previously derived expressions for the number of source degrees of freedom. The parameters that describe the lens density distribution are found by global optimization methods including genetic algorithms and particle swarm optimizers. In general, global optimizers are useful in non-linear optimization problems such as lens modeling due to their parameter space mapping capabilities. However, these optimization methods require many function evaluations and iterative approaches to the least squares problem are beneficial due to the speed advantage that they offer. We apply our modeling techniques to a subset of gravitational lens systems from the Sloan Lens ACS (SLACS) survey, and are able to reliably recover the parameters of the lens mass distribution with both analytical and regularized pixelated sources.

In the 3-dimensional curved N-body problem, the new concept of rotopulsating orbits is defined. This type of solution is used when the bodies rotate and change size during the motion. Considering the possibility of having these bodies in spaces of positive or negative curvature, it is feasible to use the following classification: positive elliptic, positive elliptic-elliptic, negative elliptic, negative hyperbolic, and negative elliptic-hyperbolic. The necessary and sufficient criteria for the existence of rotopulsators are provided. Results will be obtained that describe their qualitative behavior, which will then be applied to find examples for each type of rotopulsating orbits. / Graduate / 0280 / shimak@uvic.ca

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis describes an interferometric validation of the analytic solution for the thermal gradient which is central to numerical modelling of advanced GvVI. The bulk of the thesis, however, concentrates on the development and testing of a wavefront sensor for wavefront compensation. It also describes a Hartmann wavefront sensor that can measure wavefront changes, such as those due to substrate and coating absorption in GvVL with unprecedented precision and accuracy. According to the author it is simple to optimize and reliable, and appears very suitable for measuring wavefront distortion in advanced gravitational wave interferometers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1295719 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007

Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis describes an interferometric validation of the analytic solution for the thermal gradient which is central to numerical modelling of advanced GvVI. The bulk of the thesis, however, concentrates on the development and testing of a wavefront sensor for wavefront compensation. It also describes a Hartmann wavefront sensor that can measure wavefront changes, such as those due to substrate and coating absorption in GvVL with unprecedented precision and accuracy. According to the author it is simple to optimize and reliable, and appears very suitable for measuring wavefront distortion in advanced gravitational wave interferometers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1295719 / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2007